In the known art, cigarettes usually enter a packaging machine by way of a hopper, to which the cigarettes are fed by suitable containers or by means of a belt conveyor which conveys them in the form of a continuous layer. At the outlet of this hopper, the cigarettes are combined into groups each consisting of a number of cigarettes equal to the number in the finished packet. The characteristics of the cigarettes of each group are then checked, and those groups which comprise even only one defective cigarette are discarded.
In order to reduce the number of expelled groups of cigarettes, and thus attain considerable cost saving, a device has been proposed by the present applicant G.S. S.p.A. in U.S. Pat. No. 4,376,484, which is able to check the regularity of the cigarettes while they are still in the hopper, and to discard them before they reach the grouping station. In this device, the cigarettes are expelled from the hopper preferably by means of a pneumatic expulsion device, which directs an axial stream of compressed air against the cigarettes found to be defective, causing them to emerge through suitable apertures provided in the hopper itself. Such a device is however not free from drawbacks, it having been found that the stream of compressed air which causes the defective cigarettes to emerge generates a vortex such that at least one defect-free cigarette also emerges together with the defective cigarette.
The object of the present invention is therefore to provide a device of the aforesaid type in which the stated problems are completely nullified.
Said object is attained according to the present invention by a device for feeding cigarettes to the wrapping line of a packaging machine, comprising a hopper for feeding cigarettes to said machine, said hopper being divided lowerly into outlet channels having a width substantially equal to the diameter of a cigarette, and through which the cigarettes disposed in piles descend stepwise until they rest on a horizontal wall from which they are removed by a horizontal pusher element driven with reciprocating motion; along each of said channels there being provided, from the top downwards, sensor means for checking the cigarettes in succession, and at least one discarding device controlled by said sensor means for removing the defective cigarettes from said hopper; said device being characterised in that said discarding device is a defective cigarette extraction device disposed, with respect to said hopper, between said sensor means and said pusher element and provided, for each of said channels, with means which engage, retain and extract the defective cigarettes from said hopper and which at least during their active travel in which they extract defective cigarettes are mobile parallel to the axis of said cigarettes between two end positions spaced-apart by a distance which is equal to or greater than the length of the stroke of said pusher element; one of said end positions being within said hopper; said engagement, retention and extraction means being mobile in determined phase relationship with said pusher element.